Containers are often used to retain or store various temperature and/or pressure sensitive substances, such as aqueous solutions, peroxides, chlorines, alcohols, aromatics, ketones, and other chemically active substances. Containers storing substances that are subject to changes in pressure, temperature, altitude and other factors affecting packaging conditions require venting to avoid the negative effects that can result from retaining such sensitive substances in a container. Failure to adequately seal the liquids within the container could result in leakage. Failure to adequately vent the container may result in a pressure differential between the inside of the container and the outside of the container, which in turn may cause the container to collapse, swell or explode.
Various venting arrangements have been developed in an effort to reduce or eliminate the negative effects associated with poorly vented containers. For example, it is known to utilize a polytetrafluoroethylene (PTFE) liner or an expanded polytetrafluoroethylene (ePTFE) liner to vent a container. PTFE and ePTFE liners have a microporous structure that repels liquids while safely allowing for the free passage of gas, thus enabling their use in venting liners. These liners typically cooperate with a venting aperture located in a cap above the liner or have a number of grooves in the upper surface of the liner that cooperate with the threads of a cap to vent the container.
It is also known to combine a bottom layer of liquid-impermeable and gas-porous material with a top layer of elastomeric material, wherein the top layer defines a plurality of apertures extending through it in fluid communication with grooves furrowed into the upper surface of the top layer. When in cooperation with a container closure, the gas is vented through the apertures and then out through the grooves. An exemplary such liner is shown in U.S. Pat. No. 5,730,306.
It is known to place such prior art venting liners between a container and a closure, whereby the venting liner is supported solely by the land of the container neck, or by a combination of a land of the container neck and a cross-bar extending across the opening of the container.
One drawback associated with such prior art venting liners is that they can exhibit limited venting capacity due to constraints in the sizes of the venting apertures and/or grooves. Yet another drawback is that such venting liners can be more expensive than desired. Another drawback associated with such prior art venting liners is that, when the container closure is subject to a relatively high torque and the venting liner is subsequently subject to relatively high compressive forces, the compressible material of the venting liner can compress to a degree sufficient to exhibit a lower venting capacity than otherwise desired.
Prior art venting liners also are susceptible to undesirable deformation when subject to relatively high torque and/or compressive forces from closures due to uneven support surfaces of the container. Such unevenly-supported liners do not have sufficient rigidity to resist undesirable deformation when subjected to relatively high closure forces. Prior art venting liners have been known to wrinkle or tear, resulting in reduced efficiency and/or failure of the liner.
Accordingly, it is an object of the present invention to overcome one or more of the above-described drawbacks and/or disadvantages of the prior art.